Conceptual structure: Older children (7-9y)
Our three methods for determining how many factors to retain all suggested retaining three factors.
As in Study 1, the conceptual structure revealed by this analysis among 7- to 9-year-old children was very similar to that of adults, again characterized by a three-way distinction between BODY, HEART, and MIND.
After rotation, the first factor corresponded primarily to physiological sensations. An analysis of factor congruence confirmed that this factor was most similar to adults’ BODY factor (cosine similarity with BODY: 0.97; with HEART: 0.65; with MIND: 0.63). It was the dominant factor for such items as feel pain, feel scared, get hungry, and smell things, and accounted for 39% of the shared variance in the rotated three-factor solution.
The second factor corresponded primarily to social-emotional abilities. An analysis of factor congruence confirmed that this factor was most similar to adults’ HEART factor (cosine similarity with HEART: 0.98; with BODY: 0.66; with MIND: 0.48). It was the dominant factor for such items as feel embarrassed, feel guilty, feel proud, and feel sad, and accounted for 35% of the shared variance in the rotated three-factor solution.
The third factor corresponded primarily to perceptual-cognitive abilities. An analysis of factor congruence confirmed that this factor was most similar to adults’ MIND factor (cosine similarity with MIND: 0.96; with HEART: 0.47; with BODY: 0.62). It was the dominant factor for such items as figure out how to do things, make choices, remember things, and sense temperatures, and accounted for 26% of the shared variance in the rotated three-factor solution. (See Figure 4, Panel C, for all factor loadings.)
We consider this to be a close conceptual replication of our Study 1 findings, suggesting that by the age of 7-9 years, this three-part conceptual structure is stable and robust to a range of experimental conditions.
Attributions of mental life
In Study 1, we saw that even children as old as 7-9y—whose conceptual structure seemed to be quite similar to that of adults’—nonetheless differed from adults in their application of this concept, attributing far more of the social-emotional abilities related to the HEART to both beetles and robots. How do children’s mental capacity attributions compare to adults for the larger set of target characters included in Study 2—and what does this aspect of conceptual developmental look like earlier in development (4-6y)?
Following Study 1, we approached these questions from several angles.
First, we projected all of children’s responses into the factor space defined by adults (standardized in terms of adults’ responses), and examined factor scores by age group (again, using the method articulated by ten Berge et al., 1999). As in Study 1, this yielded three scores for each participant, corresponding, in principle, to holistic judgments of the social-emotional, physiological, and perceptual-cognitive abilities of the target character the participant evaluated. (Note that each of these three scores takes into account adult factor loadings for all 20 mental capacities, as shown in Figure 4, Panel D.)
This allowed us to examine the effects of age group (younger children, older children, adults), character (computer, robot, doll, teddy bear, beetle, bird, mouse, goat, elephant), and factor (BODY, HEART, MIND) on these scores via mixed effects Bayesian regression. As in Study 1, factor was treated as categorical variable and effect-coded, and age group was dummy-coded with adults as the baseline, to assess whether children in each age group were “adult-like” in their assessments. To explore attributions to different target characters, we included eight orthogonal contrasts: (1) animates (elephant, goat, mouse, bird, beetle) vs. inanimates (teddy bear, doll, robot, teddy bear); (2) mammals (elephant, goat, mouse) vs. other animals (bird, beetle); (3) elephant vs. other mammals (goat, mouse); (4) goat vs. mouse; (5) bird vs. beetle; (6) technologies (robot, computer) vs. toys (teddy bear, doll); (7) robot vs. computer; and (8) teddy bear vs. doll. Here we will focus on what we consider to be the contrast of the greatest theoretical interest: animates/inanimates (contrast #1).
A subset of the results of a maximal model can be found in Table 3 (see SOM for the full set of results). See Figure 5 for scores by age group, factor, and character (with a particular focus on animate vs. inaniamte characters - Panel A); and Figure 6 for scores by age (among children).
Table 3: Fixed effects from a mixed-effects Bayesian regression model predicting factor scores in Study 2 by animacy status (animates, inanimates), factor (BODY, HEART, MIND), and age group (4-6y, 7-9y, adults). The model used the formula 'factor score ~ factor * age group * animacy + (1 | subject)' and was implemented in the 'brms' package for R (Bürkner, 2017). Animacy status and factor were effect-coded; age-group was dummy-coded with adults as the baseline. Asterisks mark parameters whose 95% credible interval does not include 0.
| Parameter |
b |
Error |
95% CI |
|
| Adults |
| (Intercept) |
-0.08 |
0.07 |
[-0.23, 0.05] |
|
| HEART (vs. grand mean) |
0.03 |
0.10 |
[-0.17, 0.21] |
|
| MIND (vs. grand mean) |
0.00 |
0.17 |
[-0.35, 0.34] |
|
| characters: animates vs. inanimates |
0.49 |
0.07 |
[ 0.36, 0.63] |
* |
| characters (animates/inanimates) × HEART |
-0.26 |
0.10 |
[-0.46, -0.07] |
* |
| characters (animates/inanimates) × MIND |
-0.09 |
0.18 |
[-0.44, 0.26] |
|
| Older children vs. adults |
| age group (7-9y vs. adults) |
0.16 |
0.09 |
[-0.02, 0.34] |
|
| HEART × age group (7-9y/adults) |
0.51 |
0.09 |
[ 0.34, 0.69] |
* |
| MIND × age group (7-9y/adults) |
-0.44 |
0.09 |
[-0.61, -0.26] |
* |
| characters (animates/inanimates) × age group (7-9y/adults) |
-0.19 |
0.09 |
[-0.37, -0.01] |
* |
| characters (animates/inanimates) × HEART × age group (7-9y/adults) |
0.08 |
0.09 |
[-0.09, 0.26] |
|
| characters (animates/inanimates) × MIND × age group (7-9y/adults) |
-0.28 |
0.09 |
[-0.46, -0.11] |
* |
| Younger children vs. adults |
| age group (4-6y vs. adults) |
0.08 |
0.08 |
[-0.08, 0.22] |
|
| HEART × age group (4-6y/adults) |
0.78 |
0.09 |
[ 0.61, 0.96] |
* |
| MIND × age group (4-6y/adults) |
-0.81 |
0.09 |
[-0.99, -0.62] |
* |
| characters (animates/inanimates) × age group (4-6y/adults) |
-0.26 |
0.07 |
[-0.41, -0.12] |
* |
| characters (animates/inanimates) × HEART × age group (4-6y/adults) |
0.29 |
0.09 |
[ 0.12, 0.47] |
* |
| characters (animates/inanimates) × MIND × age group (4-6y/adults) |
-0.18 |
0.09 |
[-0.36, 0.00] |
* |
By definition, collapsing across adults’ factor scores did not differ across factors (HEART vs. grand mean: b = 0.03, 95% credible interval: [-0.17, 0.21]; MIND vs. grand mean: b = 0.00, 95% credible interval: [-0.35, 0.34]). As we would expect, adults attributed more mental capacities (collapsing across factors) to animates than inanimates (b = 0.49, 95% credible interval: [0.36, 0.63])—a difference that was diminished in the HEART domain (b = -0.26, 95% credible interval: [-0.46, -0.07]), but not substantially diminished in the_MIND_ domain (b = -0.09, 95% credible interval: [-0.44, 0.26]).
As a group, 7- to 9-year-old children’s mental capacity attributions did not differ from adults, collapsing collapsing across factors and characters (b = 0.16, 95% credible interval: [-0.02, 0.34])—but this masks several important differences between older children and adults. As in Study 1, older children’s scores were characterized by a relative over-attribution of abilities in the HEART domain (b = 0.51, 95% credible interval: [0.34, 0.69]), and a relative under-attribution of abilities in the MIND domain (b = -0.44, 95% credible interval: [-0.61, -0.26]). Collapsing across factors, older children made less of a distinction between animate an inanimate target characters, relative to adults (b = -0.19, 95% credible interval: [-0.37, -0.01]). This relative under-differentiation of animate and inanimate characters was particularly pronounced in the MIND domain (b = -0.28, 95% credible interval: [-0.46, -0.11]).
How did younger children compare to adults? As a group, 4- to 6-year-old children’s mental capacity attributions did not differ from adults, collapsing collapsing across factors and characters (b = 0.08, 95% credible interval: [-0.08, 0.22])—but again, this masks a variety of developmental differences that generally parallel the differences between older children and adults just described. Much like older children, younger children’s scores were characterized by a relative over-attribution of abilities in the HEART domain (b = 0.78, 95% credible interval: [0.61, 0.96]) and a relative under-attribution of abilities in the MIND domain (b = -0.81, 95% credible interval: [-0.99, -0.62]), and they differentiated less between animate an inanimate target characters than did adults (b = -0.26, 95% credible interval: [-0.41, -0.12]). This relative under-differentiation of animate and inanimate characters was particularly pronounced in the MIND domain (b = -0.18, 95% credible interval: [-0.36, 0.00]), and less pronounced in the HEART domain (b = 0.29, 95% credible interval: [0.12, 0.47]).
The complexities of the design of Study 2 could lend themselves to more complex models than what we have presented here, and we encourage readers to examine a model including multiple comparisons between sets of characters (e.g., mammals vs. non-mammals; technologies vs. toys) presented in the SOM. (All of the effects described above also hold true in this more complex model.)
A visual inspection of Figure 5 further clarifies these findings.
In the BODY domain, an clear animate-inanimate distinction was clearly present among 4- to 6-year-old children, though slightly attenuated (see Figure 5, Panel A, top row); a closer look at factor scores for individual characters suggests that younger children diverged from adults primarily in their attributions to the “edge cases” that were the focus of Study 1: the robot (to which they over-attributed the physiological sensations related to the BODY), and the beetle (to which they under-attributed such BODY capacities; see Figure 5, Panel B, top row).
In the HEART domain, the distinction between animate and inanimate target characters was subtler across all age groups, and the degree of distinction did not vary dramatically with age (see Figure 5, Panel A, middle row). Instead, children generally over-attributed HEART to both animates and inanimates; these over-attributions declined between 4-6y and 7-9y of age, but did not reach adult-like levels even among older children. This is consistent with Study 1, in which 7- to 9-year-old children over-attributed HEART to both the beetle and the robot, relative to adults. In this study, older children again attributed more HEART capacities to the beetle and the robot, but also to the mouse (to which adults attributed particularly few HEART capacities—perhaps because of mice’s status as vermin in this cultural context) the the goat (see Figure 5, Panel B, middle row).
Finally, in the MIND domain, neither group of children made a robust distinction between animates and inamates—but adults clearly did (see Figure 5, Panel A, bottom row). Instead, children generally under-attributed MIND to both animates and inanimates. These under-attributions became less dramatic between 4-6y and 7-9y of age, and by 7-9y children’s MIND attributions to inanimates were adult-like. But even at 7-9y, children did not attributed as many MIND capacities to animates as did adults; between 7-9y and adulthood, MIND attributions increased for all of the animate characters, and particularly dramatically for the bird, the mouse, and the elephant (see Figure 5, Panel B, bottom row).

Table 4: Fixed effects from a mixed-effects Bayesian regression model of children's responses, predicting factor scores in Study 2 by animacy status (animates, inanimates), factor (BODY, HEART, MIND), and exact age. The model used the formula 'factor score ~ factor * age * animacy + (1 | subject)' and was implemented in the 'brms' package for R (Bürkner, 2017). Factor and animacy were effect-coded, and age was mean-centered. Asterisks mark parameters whose 95% credible interval does not include 0.
| Parameter |
b |
Error |
95% CI |
|
| Collapsing across age |
| (Intercept) |
0.08 |
0.10 |
[-0.11, 0.29] |
|
| HEART (vs. grand mean) |
0.53 |
0.17 |
[ 0.19, 0.84] |
* |
| MIND (vs. grand mean) |
-0.42 |
0.24 |
[-0.87, 0.06] |
|
| characters: animates vs. inanimates |
0.31 |
0.09 |
[ 0.12, 0.50] |
* |
| characters (animates/inanimates) × HEART |
-0.16 |
0.16 |
[-0.47, 0.17] |
|
| characters (animates/inanimates) × MIND |
-0.38 |
0.23 |
[-0.84, 0.08] |
|
| Age effects |
| age (centered at the mean) |
0.08 |
0.06 |
[-0.03, 0.20] |
|
| HEART × age |
-0.11 |
0.09 |
[-0.28, 0.05] |
|
| MIND × age |
0.14 |
0.08 |
[-0.02, 0.31] |
|
| characters (animates/inanimates) × age |
-0.05 |
0.06 |
[-0.17, 0.06] |
|
| characters (animates/inanimates) × HEART × age |
-0.18 |
0.08 |
[-0.34, -0.01] |
* |
| characters (animates/inanimates) × MIND × age |
0.03 |
0.08 |
[-0.14, 0.19] |
|
A separate regression on children’s factor scores alone confirmed that, while collapsing across factors and target characters children’s overall mental capacity attributions did not vary with age (b = 0.08, 95% credible interval: [-0.03, 0.20]), the distinction between animates and inanimates in terms of attributions of HEART decreased with age (b = -0.18, 95% credible interval: [-0.34, -0.01]). (See Table 4 for the full results of this model, and Figure 6 for a visualization of changes in children’s factor scores across age.)
The raw data further supporst these observations; see Figure 7 for raw counts of no, kinda, and yes responses for all items, grouped by factor, animacy status (Panels A-C) or character (Panels D-F), and age group. For example, consider pain (the first capacity under BODY): Across age groups, most participants said that an elephant could feel pain, with the proportion of “yes” responses increasing across age groups; meanwhile, few participants said that a computer could feel pain, with the proportion of “yes” responses decreasing across age groups. More dramatic changes are evident in the HEART and MIND factors, with attributions of HEART generally decreasing across age groups (especially to inanimate target characters - e.g., the computer, the robot), and attributions of MIND generally increasing across age groups (especially to animate target characters - e.g., the mouse, the goat, the elephant). (See SOM for an analysis, parallel to the regression analyses here, of the proportion of the top-loading mental capacities for each factor that were endorsed by participants of different ages.)
